Hydrocracking process to produce gasoline and naphthenic lubricating oils concurrently

ABSTRACT

FRESH GAS OILS ARE CONVERTED TO HIGH QUALITY MOTOR FUELS AND NAPHTHENIC LUBRICATING OILS BY HYDROCRACKING AT 720-750*F. IN THE PRESENCE OF CRYSTALLINE ZEOLITE HYDROCRACKING CATALYST CONTAINING A HYDROGENATING COMPONENT, E.G., PALLADIUM, THE CATALYST HAVING BEEN PRECONDITIONED TO A PREDETERMINED STATE OF DEACTIVATION. PRECONDITIONING IS ACCOMPLISHED BY ACCELERATED COKING WITH AN AROMATIC GAS OIL AT 800-900*F.

NOV. 1973 R. l. BENNER ETAL 3,775,297

HYDROCRACKING PROCESS TO PRODUCE GASOLINE AND NAPHTHENIC LUBRICATING OILS CONCURRENTLY Filed Oct. 4, 1971 2 Sheets-Sheet 1 FIGURE 1 3 ;,I3 FEED-LA --;FRESH H2 IO |6\- GASES INVENTORS ROBERT I. BENNER WILLIAM F? MORTIMER ATTORNEY Nov. 27, 1973 R. l. BENNER ETAL 3,775,297

HYDROCRACKING PROCESS TO PRODUCE GASOLINE AND NAPHTHENIC LUBRICATTNG OILS CONCURRENTLY 1, 1971 2 Sheets-Sheet 2 Filed Oct.

INVENTORS ROBERT BENNER WILLIAM E? MORTIMER BYM U IW g ,y.

ATTORNEY United States Patent U.S. Cl. 208-111 5 Claims ABSTRACT on THE DISCLOSURE Fresh gas' oils are converted to high quality motor fuels and-naphthenic lubricating oils by hydrocracking at 720-750 F. in the presence of crystalline zeolite hydrocracking catalyst containing a hydrogenating component, e.g., palladium, the catalyst having been preconditioned to a predetermined state'of deactivation. Preconditioning is accomplished by accelerated coking with an aromatic gas oil at 800-900 F.

{BACKGROUND OF THE INVENTION One of the principal aims in the petroleum industry is to produce high octane gasoline components at high yields. This is particularly important in view of the recent eiforts to reduce and eventually eliminate the use of antiknock lead components in gasoline to avoid environmental pollution. Numerous processes produce high 0ctane components, but many times at the expense of gasoline production. Such processes often yield motor fuel of the desired quality, but at high costs due to low yields. This invention provides an integrated sequence of processing steps which produce high value gasoline in combination with a naphthenic oil from the same starting materials. 'Naphthenic oils are particularly important in industry in electrical, refrigeration, and agricultural spray applications, as well as lubricants for automotive use. The sources of naphthenic crude oil in the Western World are limited to essentially three main producing areas: (1) the States of Managas and Zulia, Venezuela; (2) offshore Peru and (3) the gulf coast of the United States. In recent years, it is known that the reserves of naphthenic crude oils have been decreasing rapidly. This process is, therefore, important in that naphthenic oils can be made available from refinery gas oils by a procedure which simultaneously yields high value gasoline.

The various known processes for producing high octane motor fuel components, such as pyrolytic cracking, hydrocracking, reforming and combinations thereof, normally are not capable of also producing a naphthenic lube oil product. g g

U.S. Pat. 3,424,671, Nicholas L. Kay, issued Jan. 28, 1969, describes a process for producing high quality motor fuel by contacting a gas oil witha preconditioned zeolite hydrocracking catalyst; containing a hydrogenation. component..'Ihe preconditioning is for the purpose of partial deactivation and .is accomplished by accelerated coking at elevated temperatures. The process decsribed in this patent recycles all of the hydrocrackate material which boils beyond the gasoline range back to the hydrocracker to extinction and does not yield any naphthenic lube oil product. In this process, the state of deactivation of the hydrocracking catalyst attained in the preconditioning step is dilierentfrom that required in the process of the present invention.

U.S. Pat. 3,142,635, H. L. Coonradt et al., issued July 28, 1964, describes a process for producing high V.I. lubricating oils by hydrocracking. A high boiling petroleum charge stock having an ASTM boiling point in excess of 850 F. is cracked over a hydrocracking catalyst such as platinum on silica-alumina. This process produces paraflinietype lube oils which require dewaxing to provide lube oils with acceptable pour points. The present invention, on the other hand, produces naphthenic lube oils essentially free of wax from hydrocarbons boiling in the gas oil range.

SUMMARY OF THE INVENTION The present invention provides a process for the conversion of straight run gas oil boiling mainly in the range 400-800 F. to high quality motor gasoline and naphthenic lube oil concurrently. A hydrocracking catalyst is used which has been preconditioned to a certain level of deactivation, as a result of which the catalyst, when thereafter used in the process, causes the formation of material higher boiling than the feed. The process comprises the following operational procedures:

(A) contacting said straight run gas oil under hydro cracking conditions, including a temperature in the range of 720 to 750 F. and a hydrogen partial pressure in the range of 800-2500 p.s.i., with a preconditioned crystalline zeolite hydrocracking catalyst containing a minor proportion of metal hydrogenating component of Group VIII, Group VI-B or mixtures thereof, said catalyst having been preconditioned by contact with an aromatic-containing gas oil under coke-depositing conditions, including a temperature above 750 F., until the catalyst has reached a degree of deactivation whereby, during said contacting under hydrocracking conditions, hydrocrackate material is produced that boils above the ASTM 90% boiling point of said straight run gas oil and that portion of hydrocrackate material of the same boiling range as said gas oil has an API gravity lower than thatof said gas oil;

(B) distilling the hydrocrackate from step (A) to obtain a gasoline product, a gas oil fraction boiling mainly in the range of 400-600 F, a lube oil fraction boiling mainly in the range of 600-800 F. and a residue, said lube oil fraction having a lower aromatic content than said straight run gas oil and having an average of at least 2.0 naphthene rings per molecule, and a viscositygravity constant of at least 0.850;

(C) and separately recovering said lube oil fraction as the desired highly naphthenic lube oil product.

Either the gas oil fraction or the residue obtained in step (B) or both can be recycled to step (A) for further conversion, and preferably both of these fractions are so recycled.

3 BRIEF DESCRIPTION OF DRAWINGS In the accompanying drawings, FIG. 1 is a schematic fiow sheet illustrating the process of the invention and FIG. 2 is a graphical representation of the effect of catalyst preconditionnig on gravity of residual hydrocrackate.

DESCRIPTION Referring now to FIG. 1 and to the preconditioning step, an aromatic gas oil boiling mainly in the range 300- 800 F. is sent through line 1 to zone 4 after having been admixed with hydrogen from line 3 and therein contacted with a conventional hydrodesulfurizing catalyst, for instance, cobalt molybdate and/or nickel molybdate on alumina, at desulfurizing conditions. Hydrogen is first introduced into the system through line 2. The effluent is passed through line 5 and admixed with additional hydrogen from line 6 if necessary and passed through the hydrocracker zone 7 containing a zeolitic hydrocracking catalyst comprising a hydrogenating component and operated under coke-forming conditions. Effluent from hydrocracking zone passes through line 8, is cooled in exchanger 9 and passes into a high pressure separator 11 through line 10. Hydrogen, methane and traces of ethane are withdrawn through line 12 to a compressor 13 for recycle. Surplus gaseous product, including hydrogen sulfide, may be withdrawn from the system through line 29. Residue from the high pressure separator 11 is withdrawn through line 14 and sent to a low pressure separator 15 wherein the hydrocrackate is stabilized to remove propane and butane through line 16 and gasoline plus residue through line 17. During preconditioning operation, effluent is withdrawn from the system through line 28 and sent to fuel storage or other uses. After the zeolitic hydrocracking catalyst has been preconditioned or deactivated, a fresh gas oil or straight run gas oil boiling mainly in the range 400-800 F. is introduced into line 1 and follows the same flow path as described previously for preconditioning; however, in this case hydrocracking conditions are used in zone 7 and the hydrocrackate from fresh gas oil is not withdrawn from the system through line 28. Instead, the hydrocrackate is conducted through line 17 and distilled in zone 18. Butane and lighter gases, if any, are removed through line 19. Gasoline boiling in the range 50-180 F. is withdrawn through line '20 and sent to storage for gasoline blending. The principal gasoline product boiling in the range of ISO-400 F. is withdrawn through line 21 and sent to storage for gasoline blending or subsequent reforming. Residue is withdrawn from tower 18 through line 22 and sent to a vacuum tower 23 wherein it is separated into gas oil boiling mainly in the range of 400-600 F. which is withdrawn through line 24, a lubricating oil fraction boiling mainly in the range 600-800 F. which is obtained through line 25 and a residue boiling in excess of 800 F. removed through line 26. The effluent from lines 24 and 26 preferably are admixed and recycled to the hydrocracker zone 7 through line 27. Alternatively, it may be desired to withdraw the gas oil boiling mainly in the range 400-600 F. through line 31 and the residue boiling mainly in the range 600- 800 F. through line 30. Both fractions may be used for applications other than for recycle to the hydrocracker zone 7. For example, the residue may be further processed to recover additional lubricating oils of higher molecular weight.

The foregoing briefly describes the process of the present invention. In further elaboration thereon, the aromatic preconditioning gas oil and/ or the fresh gas oil used for hydrocracking are passed into a hydrocracking zone 7 provided with a hydrocracking catalyst comprising essentially a crystalline alumino-silicate in combination'with a metal hydrogenating component of Group V I-B or preferably of Group VIII such as platinum or palladium. Suitable y cracking catalysts are described in US. Pat.

3,424,671. The catalyst employed in the foregoing operation is a crystalline alumino-silicate having a pore size sufi'icient to absorb benzene and with a crystallinity of at least 5% or more, preferably l0-100%, and it may contain, for example, 0.5 palladium or other hydrogenating metal component. Typically, it may have a surface area of 583 square meters/gram with 1.66% carbon as a binder.

A further elaboration of each of the operating sequences follows.

PRECONDITIONING A new or freshly regenerated zeolitic hydrocracking catalyst exhibits high activity toward destructive hydrocracking and hydroisomerization with only limited activity toward aromatization and virtually no activity toward polymerization. In addition, hydrocracking catalyst with initial high activity exhibit decreasing activity for high aromatic gasoline production over long periods of time. Therefore, in order to obtain hydrocracking at relatively constant activity and produce gasoline of essentially constant composition at substantially constant temperature, preconditioning is accomplished by accelerated coking at a temperature above 750 F. and preferably in the range of 800-900 F. with an aromatic gas oil (e.g., having 25-80 wt. percent aromatics). To measure the effectiveness of preconditioning, the degree of deactivation of the catalyst after undergoing coking in this matter was tested under hydrocracking conditions with a fresh gas oil at a desired steady-state temperature level to yield 60% conversion of hydrocrackate boiling below 400 F. API gravity and ASTM boiling point of the residual hydrocrackate are measures of the catalytic deactivation for producing high value gasoline and naphthenic lubricating oils concurrently. Steady-state temperature level is herein defined as the temperature at which 60% conversion can be maintained by adjusting the hydrocracking temperature no more than plus-or-minus 0.l F./day. Steady-state temperature levels for the hydrocracking operation on the alumino-silicate catalysts of this invention, after preconditioning, are in the range 720-750 F.

The following tabulation illustrates the properties of gas oils employed in this invention for preconditioning an alumino-silicate hydrocracking catalyst.

TABLE I.COKING FEEDSTOCK PROPERTIES Designation A B C Lt. fur- Lt. eat. Hvy. cat

Name naee oil gas oil gas oil Gravity, API 42. 7 26. 0 20. 9 Distillation:

Initial 342 398 312 EP 513 580 724 Nitrogen, p.p 1 41 50 S 1 1r, p. .m 28 1, 118 4, 300 Amhne point, F 149. 5 122. 3 Aromatics, wt. percent 30. 6 58. 7 57. 7 RA 1.2 1. 78 2. 40

1 Avg. rings per molecule of aromatic traction.

Preconditioning was accomplished by passing the foregoing gas oils or mixtures thereof over a hydrocracking catalyst at 800-870 F. and 200-300 p.s.i.g. partial pressure of hydrogen for eight hours. Following the preconditioning period, fresh gas oil was then hydrocracked at 680-730 F. to give 60% conversion.

HYDROCRACKIN G Hydrocrcaking was accomplished in zone 7 over a preconditioned commercial zeolitic hydrocracking catalyst containing 0.5% palladium in an atmosphere of hydrogen at 1550 p.s.i.g. and using fresh gas oil exhibiting the properties shown in Table II.

.stitution of TABLE II Hydrocracker feed stock properties (fresh gas oil) Gravity, API 33.2 Distillation:

Initial, F. 383 5% 457 504 50% 626 90% 745 95% 779 End point 787 Aromatics, wt. percent 28.3 CA 1 C 1 31 C 1 56 R 1 0.39 R 1 1.09 K factor 11.90 Molecular weight 270 Aniline point, F. 170.0 Sulfur, ppm. 1800 Nitrogen, p.p.m.: 52 Wax,"wt. percent 5.7

Van Nes, K. and Van Westen, H. A., Aspects of the Con- Mineral Oils, Elsevier Publishing 00., Inc., k=7 b */d; TbZCllblC ave. boiling point in F.; d=specific gravity.

The foregoing gas oil was used to determine the extent of, catalyst deactivation and as a feed stock to produce high quality gasoline and naphthenic lubricating oils concurrently by hydrocracking. Preconditioning by accelerated coking with an aromatic gas oil at high temperature and low hydrogen pressure in occordance with the procedure used in this invention renders a zeolitic hydrocracking catalyst sufliciently deactivated so that reactions such as hydrogenation, polymerization, cyclization and disproportionation can take place to produce a naphthenic oil concurrently with the production of high quality gasoline. Table III illustrates the elfect of preconditioning on hydrocracking, particularly with respect to boiling range and API gravity of the residue from hydrocrackate boiling in excess of 400 F. Preconditioning was efltected in precessive stages with the same batch of catalyst but without regenerating catalyst between successive stages. Preconditioning temperatures were in the range 843870 F. using a multiplicity of blends of gas oils shown in Table I.

TABLE Ill-EFFECT 0F PRECONDITIONING 0N HYDROCRACKING Preconditioning:

Temperature 843 850 850 870 870 Hydrogen pressure, 200 200 200 200 200 Space rate, LHSV 1.5 1.0 1.0 0.5 0.5 Coking oil percent:

A.--.---.-.---.- 100 33 50 50 30 67 50 50 Aromatics, wt. percent"..- 30. 6 39. 0 49. 4 44. 2 44. 2 RA 1. 2 1. 37 1. 59 1.8 1. 8 Duration of pretreatment,

hours 8 8 8 8 Hydrocracking:

Temperature, F). 688 698 708 726 728 Pressure, p.s.i.g 1, 550 1, 550 1, 550 1, 550 1, 550 Space rate, LHSV-.. 2.01 1.99 2.01 1. 94 1.98 Conversion/pass, percent. 59. 8 59. 0 59. 7 60. 8 59. 4 Comp. of hydrocrackate: 4

Gravity, API 49. 9 39. 8 33. 9 26. 4 26.4 Initial boiling point,

F 405 416 438 455 460 433 446 480 568 570 490 544 606 679 679 601 689 716 793 790 650 745 756 830 825 Portion in excess of 745 F., percent 0 0 0 18 17 Refractive index 1. 4407 1. 4567 1. 4693 1. 4871 1. 4876 1 Refers to feed stocks shown in Table I.

1 Average number of rings/molecule.

3 Temperature to give steady-state 60% conversion to hydrocrackate boiling below 400 F.

4 Hydrocracking temperature to give 60% conversion to hydrocrackate boiling below 400 F. from fresh gas oil shown in Table II.

6 Volume percent of hydrocrackate residue boiling in excess of ASTM point of fresh gas oil.

Data in Table III show that preconditioning of a zeolitic hydrocracking catalyst in accordance with the procedure herein described, employing aromatic coking oil, produces high boiling naphthenic hydrocarbons when the hydrocracking temperature is above about 720 F. This is evidenced in the runs made at 726 F. and 728 F., which are essentially duplicate runs, by the amounts of residual hydrocrackate boiling in excess of the ASTM 90% point of the original fresh gas oil, namely, 1718%. Thus reactions, such as polymerization or disproportionation which form high boiling material, are taking place at reaction temperatures above 720 F. A marked decrease occurs in the API gravity of the 400 F.+ hydrocrackate produced at 726 F. and 728 F., as compared with the API gravity of 400 F.+ hydrocrackate produced at 688 F. and derived by employing an incompletely conditioned catalyst. This difference in API gravity (26.4 versus 49.9) is indicative of the higher naphthenicity of the lube oil produced when the hydrocracking temperature is above about 720 F.

The method of deactivating a hydrocracking catalyst greatly influences distribution of the reaction products in residual hydrocrackate. Table IV illustrates the effect on API gravity and ASTM 90% point of the 400 F.+ hydrocrackate when the catalyst has been deactivated by the procedure herein described, as compared with normal aging of the catalyst by extended on-stream hydrocracking operations.

TABLE IV.-COMPARISON OF HYDROCRACKING ACTIVITY FOR PRO- DUCING NAPHTHENIG LUBES Accelerated Coking vs. Orr-Stream Aging Gatalyst=0.5% palladium on zeolite Feed stock=Fresh gas oil Temperature, F.=Asfiequlred for 60% conversion Pressure=1,550 p.s.i.g. 1

1 Hydrocrackate boiling in excess of 400 F. 1 By conventional hydrocracking over 18 months of continuous operation.

Inspection of Table IV and its graphical representation in FIG. 2 illustrate the importance of accelerated coking to precondition a hydrocracking catalyst for the production of naphthenic-type lube oils. Naphthenic hydrocarbons are evident in the hydrocrackate when the catalyst has been preconditioned for a steady state hydrocracking temperature of 726-728 F., as indicated by the hydrocrackate gravity of 26.4. Disproportionation and polymerization reactions have occurred under these hydrocracking conditions, as evidenced by the high ASTM 90% point of 790-793 F. compared to 745 F. for the original fresh gas oil. Curve A of FIG. 2 represents the change in API gravity of the 400 F.+ hydrocrackate with respect to steady state hydrocracking temperature for a preconditioned catalyst. At a temperature of about 710 F., API gravity of the original fresh gas oil approximates that of the 400 F.+ hydrocrackate. At a hydrocracking temperature of 726728 F., the API gravity of the 400 F.+ hydrocrackate is less than that of the original fresh gas oil indicating an increase in naphthenicity.

It will be noted from Table IV and comparison of curves A and B of FIG. 2 that a hydrocracking catalyst which has been deactivated by 18 months of continuous hydrocracking operations, has no activity for producing high boiling naphthenic hydrocarbons. API gravity and ASTM 90% point of the hydrocrackate produced by a catalyst so aged, are essentially the same over a hydrocracking temperature range of 697 F. to 745 F. Curve B of FIG. 2 represents the API gravity of 400 F.+ hydrocrackate with respect to steady state hydrocracking temperature for a catalyst which had been aged as previously described.

Table V illustrates the yield and distribution of products by hydrocracking fresh gas oil at selected temperatures by means of preconditioned catalyst.

TABLE VI.PROPERTIES OF LUBE OIL FRACTIONS TABLE V.HYDROCRACKIN G FRESH GAS OIL [Catalyst preconditioned by accelerated coking] 1 Conditions for hydrocracking: Temperature, F!

Yield and properties of products in hydrocrackate (line 17 of FIG' 1):

Yield of light products vol percen Ca and lighter 5. 33 6.14 13.30 0 18.11 23. 33 37.08 Cs- 38. 31 44. 02 46. 59 01+ 65. 78 56.40 38.86 Total 03+ 127.54 129.89 135. 84 otal 05+ 104. O9 100. 42 85. 45 Properties of 01+ (180-400 F.):

I grav' y 54.1 53.2 52.4 Paraflins, vol ercent 46.6 43.0 39. 1 N aphthenes, vol. percent 41.1 40. 7 39.3 Aromatics, vol. percent. 12.3 16.3 21. 6 Properties of 400 F. plus hydrocracki ate (line 22 of FIG. 1):

Yield, vol. percent of feed 40.2 41. 0 39. 2 API gravity 47. 9 33. 9 26. 4 Aniline poin 182 170 165 K factor 4 12. 4 11.9 11.6 Molecular weight. 215 255 280 Refractive index, N 1. 4407 1. 4693 1. 4871 Carbon/hydrogen ratio 5. 6. 46 6. 87 Carbon-type distribution and ring analysis, n-d-M method: 5

1 Preconditioning described in Table III.

2 Temperature of hydrocracking at constant conversion as catalyst activity changes. Other operating conditions on Table III.

3 VoluIm e percent of gasoline boiling below 400 F.

b 4 K= d .T =cublc avg. boiling point in F.; d=specific gravity.

Source: 1&EC 1408, 29 (1937).

6 Van Nes, K. and VanWesten, H. A., Aspects of the Constitution of Mineral Oils, Elsevier Publishing Co., Inc., 1951.

FROM HYDRO- CRACKATE (LINE 22 0F FIG. 1)

[Temperature of Hydroeracking: (726 F.)

Cut number 1 2 3 4 5 Residue Volume, percent 20 20 20 20 10 10 Density, D4 0. 8609 0. 8926 0. 9003 9052 0. 9160 Boiling range, F-. 455-616 616-659 659-701 701-759 754-793 793 Viscosity, SUS/100 39. 75 69. 39 117. 6 234. 9 540 1, 250 viscoslty, SUS/210 F 34. 92 38. 11 43. 78 53. 0 70. 46 VGC 0. 818 0. 860 0. 859 0.854 0. 856 Nn 0.4694 1. 4842 1. 4889 1. 4931 1. 4980 Molecular weight 215 232 275 308 352 408 CA 2 4 4 6 6 2 01s.. 58 65 60 54 55 59 CL... 40 31 36 40 39 39 RA--- 0.04 0.13 0. 17 0.27 0.26 0.18 RN 1. 2. 28 2. 55 2. 63 3.14 3. 76 Disposition- 2 Recycle Lubes Lubes Lubes Lubes 1 Recycle 1 Volume percent of 400 F.+ hydrocrackate. i Recycle to hydrocracking zone.

The data in Table VI show that each of the lube oil fractions boiling above 600 F., constituted an oil of the naphthenic type. These products were essentially free of waxes and hence generally do not need to be dewaxed prior to use.

The invention claimed is:

1. In a process for hydrocracking straight run gas oil boiling mainly in the range of 400 F. to 800 F. to produce gasoline, the steps for additionally producing a naphthem'c lube oil product which comprise:

(A) contacting said straight run gas oil, under hydrocracking conditions, including a temperature in the range of 720 to 750 F. and a hydrogen partial pressure in the range of 8002500 p.s.i., with a preconditioned crystalline Zeolite hydrocracking catalyst containing a minor proportion of metal hydrogenating component of Group VIII, Group VI-B or mixtures thereof, said catalyst having been preconditioned by contact with an aromatic-containing gas oil under coke-depositing conditions, including a temperature above 750 F., until the catalyst has reached a degree of deactivation whereby, during said contacting under hydrocracking conditions, hydrocrackate material is produced that boils above the AST M 90% boiling point of said straight run gas oil and that portion of hydrocrackate material of the same boiling range as said gas oil has an API gravity lower than that of said gas oil;

(B) distilling the hydrocrackate from step (A) to obtain a gasoline product, a gas oil fraction boiling mainly in the range of 400 F. to 600 F., a lube oil fraction essentially wax-free boiling mainly in the range of 600 F. to 800 F. and a residue, said lube oil fraction having a lower aromatic content than said straight run gas oil and having an average of at least 2.0 naphthene rings per molecule and a viscosity-gravity constant of at least 0.850;

(C) and separately recovering said lube oil fraction as the desired highly naphthenic lube oil product.

2. A process according to claim 1 wherein said catalyst has been preconditioned under coke-forming conditions including a temperature in the range of 800-900 F.

3. A process according to claim 2 wherein the hydrocracking catalyst is a Y-zeolite containing 0.1-1.0 weight percent palladium.

4. A process according to claim 1 wherein at least one of the fractions obtained in step (B) other than said lube oil fraction is recycled to step (A).

5. A process according to claim 4 wherein both said 400-600 F. gas oil fraction and said residue are recycled to step (A).

References Cited UNITED STATES PATENTS 3,142,635 7/ 1964 Coonradt et a1 208-111 3,405,056 10/1968 Vaell et a1. 208-111 3,424,671 1/ 1969 Kay 208111 DELBERT E. GANTZ, Primary Examiner S. L. BERGER, Assistant Examiner I 

